1. Field of the Invention
This invention is directed to an arrangement for the display of individually selectable map pictures as background information combined with overlay information comprising selectable predefined and/or operator generated symbols.
2. Description of the Prior Art
A picture display arrangement of the type indicated above may be used for operational control in military forces and in order to clarify the following description the same has been directed to this application and the problems appearing therewith. At a military formation, data are put together about the positions of one's own forces and enemy targets, fire plans, etc., in order to be used as a basis for decisions during the operation control. Traditionally this putting together of information is carried out manually by drawing symbols of one's own units and enemy targets on a map sheet. Such a method is timeconsuming and inflexible in case it should be necessary to introduce amendments. The risk of making errors when drawing is evident and the surveyability of this form of presentation is limited. In addition the handling of the map sheet itself may give rise to problems when, as is often the case, a number of adjoining map sheets must be used simultaneously.
In a prior art device a map sheet is introduced into a pocket behind a transparent, so called plasma display screen, by means of which symbols may be generated with a desirable position on the map sheet laying behind. A device of this type is an improvement as compared with the purely manual method, but the problem of changing between the map sheets and the handling of the same and the problems which arise when it is necessary to work on the "border" between two or more map sheets are left unsolved. A further problem is to obtain an exact position of the map each time it is used.
In a further prior art device the map picture is generated digitally by means of a computer. The map picture and the symbols are shown on a display screen. The picture surface comprises about 250,000 points and since it is a requirement that the map picture should be shown in color eight bits per point are required in order to obtain a good color reproduction. This means that each picture requires a memory space of about 2 Mbits. With regard to the fact that a number of map pictures, which is comparatively high, should be accessable the requirement on memory capacity is high. For this reason a device of this type will tend to be expensive. In addition the access time when changing between different map pictures will be unavoidably long due to the time used by the computer for building up each map picture.
Summarizing, the drawbacks mentioned above of the prior art devices are of a type which will have to be considered as a hindrance against an optimal use of other advanced equipment used by a modern military force.